The present invention relates to an electric device and manufacturing method of the same.
Integrated semiconductor circuits are most important electric devices which have been broadly used in a variety of fields. One of the problems from the viewpoint of reliability is the invasion of moisture or other impurities into the IC chips embedded in moulding. The invasion takes place through cracks or gaps occuring in the moulding to form paths from the outside of the moulding to the surface of the IC chip. The moisture which reaches the IC surface causes undesirable corrosion of the semiconductor constituting the IC chip and leads to malfunction of the chip.
FIG. 1 is an illustration showing how defects are formed in the packaged IC device. The structure comprises an IC semiconductor chip 29 mounted on a base frame 35, leads 37 with which the IC chip 29 is electrically coupled by means of Au wiring 39 and epoxy moulding enclosing the IC chip and lead frames 35 and 37. The surfaces of the frames have usually oxidized and formed suboxide films 24, 24' and 32 on the surface. In this structure, moisture tends to gather near the interface between the frame and the moulding. When the IC device is arranged on an electrical circuit board, soldering is performed by dipping the IC device in a molten solder at 260.degree. C. for 3 to 10 seconds. The rapid change in temperature often causes cracks in the moulding as designated by 33 and 39. Also, the moisture trapped around the frames is evaporated and causes swelling 41' to form a cavity 42 by the vapor pressure resulting in cracks 33'. This swelling is particularly likely since the oxide film 32 weakens the sticking of the moulding to the frame.